The cell culture technique of reaggregation will be used to generate cell aggregates containing both normal and neoplastic cells. The influence of neuronal and glial tumor cells on the biochemical and morphological development of normal fetal cells from rodent sympathetic ganglia and brain will be determined. The biochemical development of the normal nerve tissue will be indicated by increased activities of enzymes specific for neuron and glial cells. The influence of normal cells on the growth (cell division) of the neoplastic cells and on the possible expression of differentiated functions in the neuronal and glial tumor cells in these coaggregates will also be determined. Any enhancement or inhibition will be pursued to elucidate its biochemical nature. Furthermore, the effect of drugs that retard tumor growth on the development of normal cells in these coaggregates will be determined. The cell surface of the normal and tumor cells will be characterized and modified biochemically with the hope of correlating specific cell surface properties and the invasive behavior of different tumors.